A fire, as opposed to a smoke, detector disguised as a Christmas tree ornament is disclosed in the U.S. Pat. No. 4,075,614 to White. Fire detectors usually involve the use of heat meltable fuse or bi-metallic elements for controlling normally open alarm switches and both of which require the presence of actual flame in order to effect closing of the switches. An alarm system responsive only to the heat of actual flame is extremely dangerous since by the time the flame has effected actuation of the alarm it may be too late to prevent serious damage.
The U.S. Pat. No. 4,623,878 to Schoenwetter provides a Christmas tree mounted smoke alarm in the form of an annulus having a central opening whereby the detector may be engaged in a horizontal disposition over the very top of the tree. The detector may be disguised by the twigs at the top of the tree and also a separate ornament, such as a star may be located at the top of the tree in front of the detector to further disguise it. In neither of the above arrangements of respective fire or smoke detectors is there any means for indicating that the detectors have a positive connection with a source of power. Schoenwetter has a low-battery indicator light 44 but that is illuminated only when the battery power is low.